This invention relates to resin compositions suitable for toner. More particularly, it relates to resin compositions suitable as binder for electrophotographic toner.
2. Description of the Prior Art
In electrophotography (xerography), for fixing toner transferred onto paper or the like, there have been widely used fixing means of contact heating [such as those using a heated roller and those via a file or a belt between a heater and paper or the like (for example, JPN Patent Lay open No. 70688/1992 and No. 12558/1992)]. In these methods it is desired that the minimum temperature for fixing (hereinafter referred to as MFT) is low (low temperature fixing properties) and the temperature causing offset to that heated roller (hereinafter referred to as HOT) is high (anti-hot offset properties). Besides, thermal shelf stability is also desired so as not to cause coagulation (or agglomeration) and reduction of flowability under heat evolved from fixers within electrophotographic machines
In order to meet these requirements, there have been heretofore proposed to use toner binders having wide range of molecular weight distribution from lower molecular weight to higher molecular weight and having a glass transition temperature (hereinafter referred to as Tg) of 50.degree.-80.degree. C. (for example, JPN Patent Publications No. 20411/1995 and JPN Patent Lay-open No. 21555/1986), and to use polyester resins prepared by using oxyalkylene ether of phenolic resin of novolak type (JPN Patent Lay-open No. 27478/1993).
The above methods, however, cannot sufficiently answer to fixing properties at lower temperature required in recent high speed facsimile or copy machines, or to higher thermal shelf stability desired accompanied with miniaturization of printers.